I'm potentially thinking about buying a Tudor Sub 79190 Black Dial/Bezel in the near future. There's not many examples of this come for sale, but does someone know what a fair price would be depending on the condition, let's say good to very good (without box/papers)

 

I suggest searching for previous listings on forum classifieds, there have been quite a few sold in the past couple of years, especially on rolexforums but also on WuS. That way you can look for yourself and understand the pre-COVID19 market, price vs. condition. Just as a highly subjective opinion, I think that many people feel that the values of pieces like this, which have risen dramatically in recent times, could be hit pretty hard in a downturn. They are not Rolex.

 

I second @Dan S 's advice. recently an older example, the 79090 sold on the for sale section itself and was the rarer blue version. Take the time to gather your information.